Starship Asterisk*

by **emc** » Mon Jun 30, 2008 2:42 pm

hi bystander, Thanks for correcting me... I was unaware... there I go again!

My only excuse is the discuss/forum link wasn't where I was looking... (the missing link)

So, technically, and in my feeble defense, June 17 is the anniversary of the present day <forum/discuss> link location

here is a link to try and make up for my mistake... apropros for the coming USA holiday

by **bystander** » Mon Jun 30, 2008 2:20 pm

emc wrote:I am writing here just to thank APOD and Asterisk and wish a belated birthday to both… June 17, 2005 was the first discussion (forum) and the APOD 10th anniversary was the day before. This June 17, 2008 thread is a most fitting discussion for an Asterisk third birthday. I was pretty much blown away by the subjects herein. (Lost the ability to keep up )

While I agree wholeheartedly with your sentiments, I'm not sure about your dates. The first post to Discuss an APOD is Welcome to an APOD Discussion Forum on July 27, 2004, by Robert Nemiroff, himself. June 16, 2005, (APOD's 10th Birthday) was the first time a link was provided to the forum from APOD.
correction
The first link from APOD to Asterisk and my first introduction to Asterisk was a link inside the commentary on APOD: 2004 September 13 - Identify this Phenomenon. The discussion was Lewin's Challenge Image.

by **emc** » Mon Jun 30, 2008 1:34 pm

http://apod.nasa.gov/apod/ap080617.html

It is fun to read and write into this forum… I enjoy participating and appreciate the provisions to do so. I must admit that I am overwhelmed by the intellect that posts here but that hasn’t discouraged me from entering my penny’s worth every now and then. I try to be fun (my primary goal) and not too much a bother (I sometimes ask stupid questions

).

I am writing here just to thank APOD and Asterisk and wish a belated birthday to both… June 17, 2005 was the first discussion (forum) and the APOD 10th anniversary was the day before. This June 17, 2008 thread is a most fitting discussion for an Asterisk third birthday. I was pretty much blown away by the subjects herein. (Lost the ability to keep up

)

Kudos for the APOD works and thanks for the Asterisk playground! 8)

by **starnut** » Fri Jun 27, 2008 1:18 am

bystander wrote:
starnut wrote:I don't know about that. Time is very much a part of the spacetime. So in a collapsing universe, time will shrink to its smallest non-zero value. Was there ever a zero time before the Big Bang? One astronomer, David Darling, said that if you runs the Big Bang backward, you can slice time into smaller and smaller values but it would never reach zero.
starnut wrote:What would happen to matter and energy when time goes backward? Do we all start walking backward and regressing to embryos and then splitting to ova and sperms? Would the photons that entered our eyes back out and return to their sources? Would the steak we swallowed come out of our mouth and reconstitute into a cow? Somehow, time running in reverse doesn't make sense to me.
You seem to be arguing both sides, or is there some difference between shrinking and reversing.

Regarding the first part, I was merely repeating what astronomers were saying. Regarding the second part, I was just wondering how matter and energy would behave in a collapsing universe if time in fact will run backward or reversing as Stephen Hawking implied.

Gary

by **Arramon** » Thu Jun 26, 2008 7:19 pm

iampete wrote: Ah, ye of little faith!

Once the "Unified Theory of Everything" is perfected, someone will undoubtedly be able to figure out how to include a "reverse" gear in our transmissions (at least mathematically).

The sum of its parts... there may be a theory to encompass the 'whole' of the universe, but there will still remain the many small pieces of that whole that correspond to the individual size-scales of the universe.

But then how can you encompass something when you are lodged firmly within it? =b

We couldnt' tell our world was round until someone ventured into the seas and started sailing beyond what was known and mapped the world.

The entire fabric of our universe (consisting of the IGM and all celestial bodies) could be formed, twisted and molded to shapes of the regions they reside in, which could even be opposite of what's happening in a completely different region of the universe (anti-rotating galaxies and mergers could be driven by forces that swirl and gust through open space just as tornadoes, cyclones or hurricanes are created and fed by our own atmospheric events here on earth).

by **bystander** » Thu Jun 26, 2008 12:35 pm

starnut wrote:I don't know about that. Time is very much a part of the spacetime. So in a collapsing universe, time will shrink to its smallest non-zero value. Was there ever a zero time before the Big Bang? One astronomer, David Darling, said that if you runs the Big Bang backward, you can slice time into smaller and smaller values but it would never reach zero.

starnut wrote:What would happen to matter and energy when time goes backward? Do we all start walking backward and regressing to embryos and then splitting to ova and sperms? Would the photons that entered our eyes back out and return to their sources? Would the steak we swallowed come out of our mouth and reconstitute into a cow? Somehow, time running in reverse doesn't make sense to me.

You seem to be arguing both sides, or is there some difference between shrinking and reversing.

by **starnut** » Thu Jun 26, 2008 4:10 am

bystander wrote: Hawking believed that in a closed oscillatory universe time would necessarily go backwards as the universe collapsed. His argument in A Brief History of Time seemed well reasoned.

What would happen to matter and energy when time goes backward? Do we all start walking backward and regressing to embryos and then splitting to ova and sperms? Would the photons that entered our eyes back out and return to their sources? Would the steak we swallowed come out of our mouth and reconstitute into a cow? Somehow, time running in reverse doesn't make sense to me.

Gary

by **starnut** » Thu Jun 26, 2008 3:36 am

astrolabe wrote:Hello starnut,

Nice to here from you! The element of time is a bit of a maze if you ask me, maybe even a labrynthe that, when followed, may, in fact, return to itself. But even in that context one may return to the same place but it won't be the same time. Does there have to be an awareness of time in order for it to exist? In other words would spacetime itself exist without us? If not, then we may be more important than any of us realize!

Time exists whether we are aware of it or not. Just ask any non-human animal what time it is!

Dr. Hawkin may have a reasonable arguement for a reverse in spacetime but personally I think the universe can reverse and still there would be a foreward progress of time; mainly because I do not think that the universe would reverse exactly as it expanded (i.e. absorbed galaxies becoming unabsorbed) which I believe should be one of criteria for time reversal. Just thinking aloud here.

I don't know about that. Time is very much a part of the spacetime. So in a collapsing universe, time will shrink to its smallest non-zero value. Was there ever a zero time before the Big Bang? One astronomer, David Darling, said that if you runs the Big Bang backward, you can slice time into smaller and smaller values but it would never reach zero.

I am probably just talking through my hat anyway!

Gary

by **apodman** » Thu Jun 26, 2008 12:31 am

NoelC wrote:Ah, we are at but a shuttle stop on God's remote control.

Eureka! The reason we can't travel backward in time is because we didn't TiVo it.

by **NoelC** » Wed Jun 25, 2008 11:50 pm

Ah, we are at but a shuttle stop on God's remote control.

-Noel

by **astrolabe** » Wed Jun 25, 2008 11:47 pm

Hello starnut,

Nice to here from you! The element of time is a bit of a maze if you ask me, maybe even a labrynthe that, when followed, may, in fact, return to itself. But even in that context one may return to the same place but it won't be the same time. Does there have to be an awareness of time in order for it to exist? In other words would spacetime itself exist without us? If not, then we may be more important than any of us realize!

Dr. Hawkin may have a reasonable arguement for a reverse in spacetime but personally I think the universe can reverse and still there would be a foreward progress of time; mainly because I do not think that the universe would reverse exactly as it expanded (i.e. absorbed galaxies becoming unabsorbed) which I believe should be one of criteria for time reversal. Just thinking aloud here.

Great subject-one of my favorites!

by **apodman** » Wed Jun 25, 2008 10:25 pm

iampete wrote:... further suggestions for layman type ... material ...

Okay, here's an unusual reference. The movie (1994) is called "I.Q." and stars Walter Matthau as Albert Einstein. It's a love story between Meg Ryan's and Tim Robbins' characters who, as I recall, resemble Marilyn Monroe and Joe DiMaggio. Einstein spends much of the movie (once again from my recollection) demonstrating the principles of Relativity to the Marilyn character using props like toy trains. All the time, a Navaho (who believes that the center of the universe moves with him wherever he goes) stands silently and symbolically outside on a ledge. Abstract art about the abstractions of science and whatever else.

From the movie, according to imdb.com ...

Boris Podolsky: James! How's the rat business?
James Moreland: Well, actually it's mostly students I'm experimenting on now.
Kurt Godel: My God, the mazes must be enormous.

by **bystander** » Wed Jun 25, 2008 12:58 pm

starnut wrote:I would say that time is an abstract concept that only the human intellect is aware of. Is there any other animal that is aware of the past, present, and future? Without time, there can be no universe because it would remain a singularity indefinitely. Once the Big Bang happened, there was no going back, so time can flow only in one direction. Whether this is true in an oscillating universe where the expansion stops and everything reverses direction back to a singularity, to be reborn in another Big Bang, I have no idea. So far the evidences seem to point to the universe expanding forever, ending either in the Big Chill or the Big Rip. In that case, time will go forward forever even after the universe dies out.

Hawking believed that in a closed oscillatory universe time would necessarily go backwards as the universe collapsed. His argument in A Brief History of Time seemed well reasoned.

by **starnut** » Wed Jun 25, 2008 3:37 am

apodman wrote:
iampete wrote:someone will ... include a "reverse" gear in our transmissions
I'm more looking for an elevator where you can request a specific floor. And, unlike space, time can have absolute coordinates without ruining the theory, I think.

But, before I carve the oars to row against the current of time or build the machinery to redirect a piece of it, I need to know a few things starting with this: Is the forward flow of time a driving phenomenon, a driven phenomenon, just the abstract string that connects all the moments in time, just a physical rule without physical cause that comes with the universe, or something else? Take your "time" on this one.

I would say that time is an abstract concept that only the human intellect is aware of. Is there any other animal that is aware of the past, present, and future? Without time, there can be no universe because it would remain a singularity indefinitely. Once the Big Bang happened, there was no going back, so time can flow only in one direction. Whether this is true in an oscillating universe where the expansion stops and everything reverses direction back to a singularity, to be reborn in another Big Bang, I have no idea. So far the evidences seem to point to the universe expanding forever, ending either in the Big Chill or the Big Rip. In that case, time will go forward forever even after the universe dies out.

Just my 2 cent worth of speculation. 8)

Gary

by **apodman** » Wed Jun 25, 2008 1:27 am

iampete wrote:someone will ... include a "reverse" gear in our transmissions

I'm more looking for an elevator where you can request a specific floor. And, unlike space, time can have absolute coordinates without ruining the theory, I think.

But, before I carve the oars to row against the current of time or build the machinery to redirect a piece of it, I need to know a few things starting with this: Is the forward flow of time a driving phenomenon, a driven phenomenon, just the abstract string that connects all the moments in time, just a physical rule without physical cause that comes with the universe, or something else? Take your "time" on this one.

by **iampete** » Tue Jun 24, 2008 11:48 pm

apodman wrote: . . . Is there a cosmologist among you who doesn't believe that time goes only forward? I'm kind of surprised we haven't heard from any fans of negative time yet.

Ah, ye of little faith!

Once the "Unified Theory of Everything" is perfected, someone will undoubtedly be able to figure out how to include a "reverse" gear in our transmissions (at least mathematically).

by **Andy Wade** » Tue Jun 24, 2008 11:12 pm

apodman wrote:
iampete wrote:... my 35 year old math and physics texts ...

henk21cm wrote:... at least 35 years ago that i had to deal ...

apodman wrote:... 33 (!) years ago ...
Is there a cosmologist among you who doesn't believe that time goes only forward? I'm kind of surprised we haven't heard from any fans of negative time yet.

I started counting backwards on my fortieth birthday and I'm now 30 years old... again... if that's what you mean.

by **apodman** » Tue Jun 24, 2008 11:03 pm

iampete wrote:... my 35 year old math and physics texts ...

henk21cm wrote:... at least 35 years ago that i had to deal ...

apodman wrote:... 33 (!) years ago ...

Is there a cosmologist among you who doesn't believe that time goes only forward? I'm kind of surprised we haven't heard from any fans of negative time yet.

by **henk21cm** » Tue Jun 24, 2008 9:15 pm

iampete wrote: From the text: ". . . the Milky Way . . . is not near any center (expansion models do not allow for a discoverable center) - a positional state that may not even be valid (one can however speculate about the spatial distribution of galaxies relative to the singularity which doesn't have a location since the space associated with this Universe did not exist until after the Big Bang)." (emphases mine)

For us, living in a 4-D universe, that is a valid assumption or thesis. <Speculation mode=on> For a being in a 5-D universe, observing us 4-D 'flatlanders', it might be evident, similar as for 3-D people, watching a 2-D baloon being blown up and seeing black spots on the baloon getting further an further away. The 2-D people on this baloon see their universe expand. The 2-D baloon has a 3-D center. Similarly our 4-D 'baloon' may have a 5-D center. Still for the 4-D 'flatlanders' there is no special point, since we do not grasp the fifth dimension. Their (4-D people) entire observable universe expands, with no special point. It is minimally 5-D, however might be higher. <Speculation mode=off>

Hope this helps.

Another attempt to get you a mental picture is the phase space, the 6N dimensional space of all x, y, and z components of postion and impuls vectors of an N particle system. It is a pure mathematical idea; quantum physics heavily relies on the phase space. The Hilbert method (based on the Gramm-Schmidt orthogonalization process) for the construction of such a space may be helpfull, to built one on paper. I can't produce one for you now, it is at least 35 years ago that i had to deal with this stuff, so all is 'heavily corroded'.

No, i'm not drunk, nor high, although when you read this post, you might think i am.

_______________________
Henk

by **iampete** » Tue Jun 24, 2008 8:49 am

apodman wrote:(lots of info and recommended reading)

Thanks again for your posts. Google and other research it is.

It's also quite frustrating to me that my 35 year old math and physics texts have become much less intelligible than they were when new.

by **apodman** » Tue Jun 24, 2008 12:49 am

iampete wrote:If one takes a projection of a 3-D sphere onto a 2-D surface, one can determine the center of the 2-D projection. Why would that analogy not work when trying to project a 4-D sphere into the 3-D space that we observe?

What works for the 3- and 2-D case will work for the 4- and 3-D case, as well as for the simple 2- and 1-D case which simply projects the circumference of a circle onto a line segment.

But I don't think of the expanding 4-D supersphere (with time as its radius and space dimensions as its 3-D supersurface) as the shape of the universe. I think of it as a geometrical convenience that sets the time dimension perpendicular to space in the present day, merges a model of four dimensions with a model of expanding space, and places the big bang at a singular point in the 4-D center. If you want to know how far this analogy goes, you need only ask where we look for the parts of 3-D space closest to this singular point in the center. The answer is that we look as far away as we can in any direction. So now the center is all around and we're in the center of it. The universe is inside out.

So I'm not sure what exactly your proposed projection corresponds to in the physical universe, and I have the same old problem with it anyway: If I am to believe in Einsteinian spacetime (even though "it just don't seem natural"), I must reject any line of thinking that depends on talking about an absolute position in 3-D space, and I think you need one to choose the orientation for your proposed projector and screen, so to speak. Anyway, your projection would tell you what orientation you chose, not what you want to know about the space (which I think is unknowable because it's not there).

The more I wing it, the less I know. I think I'll stop here.

iampete wrote:If you have further suggestions for layman type reading material beyond what you provided earlier, I'd be interested to see them.

Special Relativity, General Relativity, Cosmology ...

Special Relativity only took Einstein nine pages to describe completely. My textbook was a paperback less than a half inch thick (Introduction to Special Relativity by Robert Resnick) and we did it in a half semester of a three-credit course. The book made it easy with illustrations, exercises, and I believe problems with answers. Used ones are cheaper than new ones, and the ones at the library are cheaper yet. After that book, the translated original Einstein was clear when I read it. For less technical, there's TV documentaries galore on Special Relativity. For more technical, some of us get state university classes on a free cable TV station. Any layman with an open mind and a little math can grasp Special Relativity completely.

There is no simple nor intuitive way to describe the blood and guts of General Relativity, and I'm sorry to have nothing to recommend. Even if they describe it well, it comes out lengthy (Hawking) or over my head in its brevity and heavy math (Einstein). Some TV documentaries about black holes, etc. may be worth a look.

Cosmology articles, not too technical nor non-technical, appeared regularly in Sky & Telescope during the years I had a subscription. I don't know how it is today.

These days I mostly use google to find stuff on the internet. You need to pick through the results for something good, though.

by **iampete** » Mon Jun 23, 2008 6:57 pm

Arramon wrote:http://www.fas.org/irp/imint/docs/rst/Sect20/A8.html
. . .

Thank for the fas.org link - mostly understandable and helpful stuff.

From the text: ". . . the Milky Way . . . is not near any center (expansion models do not allow for a discoverable center) - a positional state that may not even be valid (one can however speculate about the spatial distribution of galaxies relative to the singularity which doesn't have a location since the space associated with this Universe did not exist until after the Big Bang)." (emphases mine)

Apparently, I'm not the only one barking up this possibly non-existent tree. While the specifics will undoubtedly remain forever beyond my comprehension, I remain optimistic I'll eventually get a conceptual grasp --- there's apparently a lot of info available to be followed up; I just need to find time to get to it all!

by **Arramon** » Mon Jun 23, 2008 5:51 pm

http://www.fas.org/irp/imint/docs/rst/Sect20/A8.html

Another commonly cited "mental picture" is the raisin loaf analog. Consider bread dough(with a high dosage of yeast) in which are embedded randomly but uniformly spread out numerous raisins. The dough (envision this either in the traditional shape or as a sphere) is then baked in an oven. As it cooks, the entire loaf expands outward indefinitely (in reality this process will eventually stop). With growth, the raisins become progressively farther apart but the individual raisins largely retain their original size. During expansion the raisins farthest from any one chosen as a frame of reference will move the most and hence at a faster clip (velocity) than those close to each other. While helpful in the visualization, this model too has problems. The raisins near or at the edges do not see raisins in all directions, only inward, which violates the Cosmological Principle. And, as one stands back from the baking loaf, the bread "universe" has a conceptual center. So then, this analog is imperfect and aids only in envisioning a part of the expansion picture.

Let's delve into a pictorial way to visualize this notion of expansion with the help of this diagram which presents the process as a 2-D portrayal using circles (the concept depicted works just as well for the 3-D [balloon] version):

The circle on the left depicts a sphere with a radius r1 on which a coordinate system (essentially, latitude and longitude lines) has been traced. That describes expansion from an initial point (radius r0). As expansion continues, the circle on the right now has a radius r2. The coordinate system has correspondingly expanded so that the coordinates of any point, such as locate any of the three "Saturn" discs (note that they remain constant in size even as they separate; this is analogous to the above-mentioned statement that galaxies do not expand in proportion to space expansion), have changed only in scale. From this one can define a basic function called the Scale Factor, given by the symbol R, which describes the changes in dimensions (three-dimensional lengths) in an expanding system as a function of time. This simple equation applies: R(t) = rn/r0, where rn is the radius at some specific time and r0 is the initial radius (for the Universe, the singularity point). Thus, the amount or rate of expansion (or contraction) can be adjusted by a given Scale Factor; if not defining a linear function one value will yield a faster (slower) rate than another that is numerically less (greater). For a given span of time, separations (length spreads) will be greater for higher R's than lower ones. The coordinates are said to be co-moving, that is, they enlarge during expansion but all x, y, and z points referenced to them scale proportionately with R while maintaining their same relative positions. The Scale Factor is a fundamental geometric property that is relevant to a description of an expanding Universe.

Four general modes of change of R with time are depicted in the next diagram. Note that in three of the four cases shown R varies in magnitude with time.

Graph a shows a decreasing rate of expansion, b a uniform or constant (linear) rate, c, an increasing rate, and d a negative rate of expansion (i.e., a contraction).

Note that for a given increase in expansion over some time from t1 to t2, points that are farther apart at t1 expand at progressively greater velocities than those nearer each other; thus, they cover greater distances in a unit of time (we shall see on the next page that this ever increasing velocity outward is associated with progressive increases in wavelengths of light as shown by the redshift phenomenon).

This can be further elucidated with this diagram:

Let the upper row represent the position of three galaxies at t1 and the lower the later expanded location at t2. The elapsed time is (t2 - t1) = Δt (Delta t = a finite interval of time). Initially, each galaxy is separated by a distance d. Following expansion, A is now separated from B by 2d and from C by 4d. Therefore B has moved with respect to A (the observation position) at a recessional velocity (d/t) of (2d - d)/Δt = d/Δt and C from A at (4d - 2d)/Δ t = 2d/Δ t. Thus, the velocity of recession of C with respect to A is twice that of B to A. (Returning to the balloon analogy, one can see that farther dots recede faster than closer ones relative to some dot chosen as the point of observation.) The relative velocities will depend on the Scale Factor. As determined from red shift studies (next page), in this dynamic Universe any two galaxies are moving relative to one another at different recessional velocities which depends on their distance apart; the velocity between one of these galaxies and still a third that is twice as far away will be double (twice) that of the first pair considered.

Some of the recent ideas on the start times for the first stars and galaxies received support and specificity from the WMAP results. The first stars began to form as Supergiants about 200,000,000 million years ago. The first galaxies began to organize some three hundred million (300,000,000) years later. This diagram depicts these stages (from top): 1) initial stages of CBR variations; 2) clots of dark matter prior to organization as stars; 3) the first supergiants; 4) developing galaxies; 5) galaxies after the first billion years.

The time lines for the first stars and galaxies as measured by different space telescopes (JWST is the James Webb Space Telescope planned for 2010; its mission will focus on the early eons of the galaxies, so that the starting time shown above is a "best estimate" for now) are shown in this diagram. Of special import is the new estimate of when the first stars started to form - about 200 million years after the Big Bang.

the pictures help more than all that scientific babble... =/

by **iampete** » Mon Jun 23, 2008 7:20 am

apodman wrote: . . . A 3-D sphere has a 3-D center, but its 2-D surface has no preferred 2-D center point on that surface.
Likewise, a 4-D supersphere has a 4-D center, but its 3-D supersurface has no preferred 3-D center point on/in that supersurface. . .

Thanks, that makes sense to me; I can even comprehend a "picture" of that in my mind!

Yet, there's still a conceptual disconnect here for me. If one takes a projection of a 3-D sphere onto a 2-D surface, one can determine the center of the 2-D projection. Why would that analogy not work when trying to project a 4-D sphere into the 3-D space that we observe?

apodman wrote: . . . I'm not sure, but I also think there may be a problem with your turning the 0,0,0 space coordinates into i,j,k values over time. We might be violating one of the ideas of Einsteinian spacetime again by thinking of i,j,k as absolute positions with respect to the origin point rather than positions that can only be measured relative to other positions.

This I have a problem with, even at a conceptual level. I will continue to do some more reading to see if I can find something helpful to me. To date, all the stuff I've been able to find is either too elementary to satisfactorily explain anything or way beyond my comprehension level. If you have further suggestions for layman type reading material beyond what you provided earlier, I'd be interested to see them.

I appreciate your helpful and non-condescending responses in all your previous replies.

by **Qev** » Mon Jun 23, 2008 6:41 am

NoelC wrote:Why were insects so large 100 million years ago?

The paleontological record suggests that the oxygen content of the atmosphere was as high as 30% during some periods (instead of the 21% we have now), which would support much larger insects than we have today.

Why does the Earth go through ice ages?

Changes in solar output, Earth's orbit and axial orientation, changes in the composition of the atmosphere, the configuration of the continental land masses... it's a confluence of many factors.

I see no reason to conclude subtle things aren't happening. Does the incredible red shift of ultra-distant quasars indicate they are moving away, or maybe just that they emitted light at a different frequency (relative to today) back then.

Changing the frequency of the emitted light won't change the positions of the absorption spectra, the way redshift does. Also, if physics was different enough back then to alter the way the objects we observe emit light, then it would probably be different enough that the objects couldn't be there to emit the light in the first place... or at least not in the form we observe them.

Any of this is probably moot, insofar as virtually all the things that we put labels on - those things we hold as constants in our brains: Distance, time, dimensions, etc. - are just the observed effects of something else in our tiny little corner of the cosmos at this moment in time, anyway.

It could be even worse, if the Holographic Principle holds.

Starship Asterisk*

Eta carinae & the Homunuculus Nebulae (APOD 17 Jun 2008)

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